1. Related Fields
Artificial body members used in knee and other joint arthroplasty, and systems and methods using the same, for tensioning ligaments, tendons or other soft tissues.
2. Related Art
There are currently three total knee arthroplasty (TKA) cruciate ligament options available to surgeons. A first option is to sacrifice both the posterior cruciate ligament (PCL) and the anterior cruciate ligament (ACL). A second option is to retain the PCL and sacrifice the ACL. A third option is to preserve both cruciate ligaments. Generally, the first and second options are more common, because most patients having indications for total knee arthroplasty also typically have an ACL deficiency. For younger and more active patients with a healthy posterior cruciate ligament, it may be desirable in some instances to select the second or third option and retain at least the PCL. In doing so, stability may in some cases be achieved with the patient's own ligamentous soft tissue, instead of the implant.
Referring now to FIGS. 1, 2A, and 2B, there are typically two approaches to retaining the PCL during total knee arthroplasty. To this end, surgeons may resect the entire proximal portion of the affected tibia (10) as shown in FIG. 2A, or may resect most portions of the proximal tibia, leaving only a small area (12) of protruding bone and cartilage (13, 15, 17) at the posterior portion as shown in FIGS. 1 and 2B. Because the PCL (20) has an attachment point (16) that is slightly inferior to the resection plane (14), the PCL (20) usually stays attached to the tibia (10) regardless of which method is used. The benefits and disadvantages for each of the PCL-sparing resection techniques shown in FIGS. 2A and 2B have been widely debated. It has been suggested by those in the art that the function of the PCL changes with removal of the bone above the PCL attachment to the tibia.
Many surgeons find it difficult to leave a small area (12) of protruding bone and cartilage (13, 15, 17) at the posterior portion of a proximal tibia (10) due to the location of the PCL and surrounding bony structure. In fact, many surgeons prefer a total proximal resection (14) because it takes less practice and decreases operating time. In addition, it is generally very easy to notch the small area (12) of remaining bone or accidentally cut it off. Therefore, the approach of many surgeons is to resect the entire proximal tibia (10) in the first place as shown in FIG. 2A.
The problem associated with the PCL-sparing technique of resecting the entire proximal tibia as shown in FIG. 2A is that it may affect laxity, stiffness, tension, and other kinematic factors of the PCL (20). Essentially, by removing the small area (12) of protruding bone and cartilage (13, 15, 17), the tension (T) in the PCL may be reduced and forces associated with the PCL may be altered. Additionally, some of the edges of the PCL (20) may be inadvertently cut along the resection plane (14), thereby increasing elasticity of the PCL due to a smaller diameter. A loose PCL may affect anterior-posterior stability of the femur in relationship to the tibia (10) and may defeat the purpose of retaining the PCL in the first place.
Another problem associated with some PCL-sparing techniques involving resecting the entire proximal tibia occurs during trial reduction. Tibial inserts of the patient's size and having different thicknesses are typically placed between the femur and tibia until the best possible stability throughout a full range of motion is achieved. Unfortunately, an appropriately sized insert may over-stretch the PCL, or under-stretch the PCL, leaving the surgeon to make compromises. Often, if the PCL is over-stretched or placed in too much tension after an appropriate insert thickness is selected, invasive and difficult soft tissue and ligament releasing is performed. Alternatively, if the PCL is too loose, under-stretched, or insufficient for stability, a deep dish cruciate-retaining insert or a posterior stabilized implant may be used.